You won't be able to do it unless you are "buddies" with the person you are addressing, you would have to submit a buddy request to them (or they would need to do that to you) and the other party would need to accept it. It is my understanding that some people won't accept a buddy request without an introductory PM first, but that isn't a requirement, just personal preference.

But yeah, I personally think it is a bit weird; I don't see anything to additionally be gained in doing that which can't be accomplished by sending a PM instead, and at least that's private, where guest books are readable and the conversation can be followed by anyone who happens along to view your profile. It's more private than forum posting, but only by obscurity, not security...

Then again, I don't really understand the appeal of social media at all myself, having neither a Facebook or Twitter account, so maybe I'm not the best one to give out advice.

You won't be able to do it unless you are "buddies" with the person you are addressing, you would have to submit a buddy request to them (or they would need to do that to you) and the other party would need to accept it. It is my understanding that some people won't accept a buddy request without an introductory PM first, but that isn't a requirement, just personal preference.

But yeah, I personally think it is a bit weird; I don't see anything to additionally be gained in doing that which can't be accomplished by sending a PM instead, and at least that's private, where guest books are readable and the conversation can be followed by anyone who happens along to view your profile. It's more private than forum posting, but only by obscurity, not security...

Then again, I don't really understand the appeal of social media at all myself, having neither a Facebook or Twitter account, so maybe I'm not the best one to give out advice.

it can be awkward for everyone to see, when visiting someone else's profile, but, with few characters and the notion that all can read. to be honest, it's not that big of a deal. I typically use mine to drop off things here and there, I don't do the buddy thing and I don't see the point to private messages, but the option is there for those who are interested. regardless, it's your call in the long run, I was doing the buddy/guest book option but then I lost interest in it. but if you have an open twitter/facebook/other then there really isn't much difference from guestbook posting. it's very similar to twitter due to character limits. you don't have to use the feature, it's just there for a quick jot between friends.